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NEWSCIENCENEWSCIENCENEWSCIENCE Control Circuit Figures 3 and 4 show a simple circuit to control and drive this mini-system. You are going to make a ‘square pulse’ signal that 'plays' the electrodes like a tuning fork and which you can watch on an oscillo- scope. The premise given by the literature is that the faster you want do go down the road, the ‘fatter’ you make the pulses going into the reaction chamber. Duty cycle will vary with the throttle in the vicinity of 90% mark — 10% space (off/on). There is nothing sacred about how the pulse waveform is generated; there are many ways to generate pulses, and the attached diagrams show a few. Figure 4 gives the NE555-circuit approach from the referenced patent. The output switching transistor must be rated for 1-5 amps at 12 volts DC (in saturation). Go with a plan that works for you or your friendly neighbourhood technoid or epoxy * reaction chamber with electrodes and fittings * 3/8" stainless steel flex tub- ing, fittings and clamps ¢ carb/FI vapour- pressure fitting kit * pressure, CHT (or EGT) and level gauges * stainless steel valves * copper mesh junction * ceramic surface treatment for cylinders and pistons inless steel or ceramic-treated exhaust assembly ¢ drill, screwdriver and pliers ¢ hole cutter * wire wrap, solder iron and clippers * DVM and oscilloscope. mechanic, and go get all the circuit ele- ments, including the circuit board, IC sock- ets and enclosure/box, from your local electronics store such as Radio Shack or Circuits-R-Us. DigiKey has better selec- tion, service and knowledge, plus they have no ‘minimum order’ requirements. Be sure to use a circuit board with a built-in ground plane, and to accommodate room for mounting two or three of the gauges. Make sure to get spec sheets on any IC you use. More details of the best circuits to use will be announced, pending prototype testing. Mounting the reaction chamber in the engine compartment will require running a stub to your pressure gauge where you can watch it. You can easily make 30-gauge wire-wrap connections between the socket pins and through-hole discrete components having wire leads. Reaction Chamber Construct as shown in figure 2. Use a section of 4" PVC waste pipe with a threaded screw-cap fitting on one end and a standard end-cap at the other. Make sure to drill and epoxy or tap threads through the PVC components for all fittings. Set and control the water level in the chamber so that the water submerses the pipe electrodes well; yet leave some head- room to build up the hydro- gen/oxygen vapour pressure. Use stainless steel wires inside the chamber, or other- wise use a protective coat- SS ing; use insulated wires out- fuse side. + Ensure that the epoxy per- fects the seal, or otherwise bat lay down a bead of water- proof silicone that can hold - pressure. You will want to get your chamber level sen- throt sor verified before you epoxy the cap on. The screw fitting may require soft silicone sealant or a gasket. Its purpose is to hold pressure and allow — periodic inspection of the tank electrodes. No leaks, no level problems. sensor Make sure you get a sym- — metric 1-5 mm gap between the two stainless steel pipes. The referenced literature chamber suggests that the closer to 1 lavel mm you get, the better. Sensor Make your solder connec- tions at the wire/electrode junctions nice, smooth and solid. Then apply a water- proof coating, e.g., the epoxy you use for joining the pipes to the screw-cap. This epoxy must be waterproof and capable of holding metal to plastic under pressure. adj. frequency tank level Figure 3 APRIL — MAY 2002 NEXUS ¢ 49 www.nexusmagazine.com